Sperm maturation in the epididymis requires epithelial gene products, expressed in a region specific pattern. The long-term objective of this proposal is to discover the mechanism underlying the maintenance of segmental function in the adult epididymis. We hypothesize that hox genes are master regulators of this process. Hox genes are known to be crucial in segmental patterning of the embryo but adult function is unknown. Expression levels of selected hox genes will be studied in the adult mouse epididymis using RT-PCR and Northern analysis. Regional differences and cellular localization of hoxa-11 protein, specifically, will be studied with Western blot analysis and immunohistochemistry, respectively. The same methods will be used to examine for Meis 1, a known DNA-binding cofactor for hox genes, and for the cell adhesion molecule L1-CAM, a potential downstream target for hoxa-11 protein. Interaction of hoxa-11, cofactor and downstream target in the adult rat epididymis will be analyzed by Electrophoretic Mobility Shift Assay. These studies investigate a novel, specific pathway relevant in the maintenance of functional segmentation of the epididymis. This information will provide new insights into epididymal function, important to the understanding of male fertility and infertility.